Preparation method of large-area hexagonal boron nitride ultraviolet single photon source

Abstract

The invention discloses a preparation method of a large-area hexagonal boron nitride ultraviolet single photon source, which comprises the following steps of: fixing a silicon carbide substrate by using a graphite clamp in a vapor deposition furnace; the system is firstly vacuumized to the air pressure below 10 <-3 > Pa, then is heated to the reaction temperature and is subjected to heat preservation; the method comprises the following steps: preparing a graphite clamp, introducing two raw material gases, namely BCl3 and NH3 or BF3 and NH3, promoting the graphite clamp to slightly decompose by utilizing a high-temperature environment so as to provide a carbon source, mixing the gases and carrying out chemical reaction, growing a large-area hexagonal boron nitride film with carbon defects, and stripping the film from a substrate, namely the hexagonal boron nitride ultraviolet single photon source. The large-area hexagonal boron nitride ultraviolet single-photon emission source is successfully prepared, a potential emission center presenting the single-photon source characteristic is represented, a way is laid for practical application of the hexagonal boron nitride material in quantum communication and photoelectron application, and the stability and efficient single-photon emission capacity of the material at the room temperature are shown.

Description

Technical Field

[0001] The invention relates to the technical field of single-photon sources, and in particular to a method for preparing a large-area hexagonal boron nitride ultraviolet single-photon source. Background Art

[0002] Optical applications with single photons play a crucial role in the development of future quantum computing and information processing technologies. To enable the effective application of these technologies, single-photon source systems need to be stable over long periods of time, easy to set up, and preferably made of low-cost materials. Current research is focused on finding new single-photon sources that have different emission wavelengths and higher emission rates and can be excited by other means besides lasers, such as electric current (electroluminescence) or fast electrons (cathodoluminescence, CL).

[0003] Semiconductor quantum dots as well as color centers in diamond and silicon carbide have provided solid-state platforms for optically stable room-temperature single-photon emitters in the visible range. In recent years, low-dimensional layered semiconductors have attracted attention as an emerging promising optical material. Single-photon sources have also been recently described in transition metal dichalcogenides and hexagonal boron nitride (h-BN). Quantum communication is usually achieved by transmitting (single) photons in optical fibers, but free-space links are also considered as a viable alternative. One advantage of the UV spectral range is that its background solar radiation is very limited, so optical communication can be carried out during the day. However, due to the technical difficulties in preparing wide-bandgap nanostructures with single-photon source properties, there have been few reports on UV single-photon sources to date. Although UV single-photon sources operating at 200K have been achieved using GaN and InGaN quantum dots, the synthesis of such color centers in wide-bandgap materials may be a more feasible route to achieve room-temperature UV single-photon sources.

[0004] h-BN has recently become a promising candidate for optoelectronic applications due to its strong UV radiation that is stable at room temperature. The luminescence of high-quality crystals is mainly manifested as a sharp deep-UV line at 5.75 eV. In addition, other strong features in the UV spectral region are related to extrinsic defects, but the quantum nature of these emissions has not been fully explored so far. In addition, in previous studies, people have not been able to effectively obtain large areas of h-BN with UV single-photon emission. Summary of the invention

[0005] The present invention provides a method for preparing a large-area hexagonal boron nitride ultraviolet single-photon source, and successfully realizes a large-area (6-inch) h-BN ultraviolet single-photon emission source. This breakthrough paves the way for the practical application of h-BN materials in quantum communication and optoelectronic applications. The present invention demonstrates the stability and efficient single-photon emission capability of the material at room temperature, which will provide important support for the development of future quantum technology.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A first aspect of the present invention provides a method for preparing a large-area hexagonal boron nitride ultraviolet single-photon source, comprising the following steps:

[0008] Step S1: In a vapor deposition furnace, a graphite fixture is used to fix the silicon carbide substrate and the vacuum is evacuated to 10 -3 Pa pressure or less;

[0009] Step S2, then using resistance heating to raise the system temperature to the reaction temperature and keep it warm; in a high temperature environment, two raw material gases, BCl3 and NH3, or BF3 and NH3, are introduced. The high temperature causes the graphite fixture to slightly decompose, thereby providing a small amount of carbon source. In the middle of the deposition chamber, the gases mix and react chemically, growing a large area of ​​hexagonal boron nitride film with carbon defects;

[0010] Step S3, then turn off the power, cool the hexagonal boron nitride film and the substrate to room temperature and then take them out of the furnace, peel off the hexagonal boron nitride film from the substrate, and obtain a large-area hexagonal boron nitride single-photon source.

[0011] Furthermore, the growth time of the hexagonal boron nitride film in step S2 is 80 to 120 minutes.

[0012] Furthermore, in step S2, the system is heated to 1500-1700° C. and kept warm.

[0013] Furthermore, in step S2, the volume ratio of the two raw material gases BCl3 and NH3, or BF3 and NH3, is 1:0.9.

[0014] Furthermore, in step S2, the two raw material gases BCl3 and NH3, or BF3 and NH3, enter the deposition chamber from the bottom.

[0015] The second aspect of the present invention provides a large-area hexagonal boron nitride ultraviolet single-photon source, which is prepared by the above-mentioned preparation method of the large-area hexagonal boron nitride ultraviolet single-photon source.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] Hexagonal boron nitride has become a promising candidate for optoelectronic applications due to its strong and stable ultraviolet radiation at room temperature. Although it has many sharp spectral features in the ultraviolet region, the single-photon source characteristics of these features have not been clearly studied. The present invention successfully realized a large-area h-BN ultraviolet single-photon emission source and characterized the potential emission centers (including 4.08eV, 3.93eV, and 3.74eV centers) that exhibit single-photon source characteristics. This breakthrough paves the way for the practical application of h-BN materials in quantum communications and optoelectronic applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 a is a physical picture of a 6-inch hexagonal boron nitride film after peeling in Example 1 of the present invention;

[0019] Figure 1 b is the CL spectrum of the hexagonal boron nitride film in Example 2 of the present invention, Figure 1 c is the second-order time correlation function;

[0020] Figure 2 This is a high-resolution TEM image of the hexagonal boron nitride film in Example 3 of the present invention. DETAILED DESCRIPTION

[0021] The specific embodiments of the present invention are further described below. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0022] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are commercially available unless otherwise specified.

[0023] Example 1. Preparation method of large-area hexagonal boron nitride single-photon source

[0024] This embodiment is used to provide a method for preparing a large-area hexagonal boron nitride single-photon source of the present invention. The preparation method uses a chemical vapor deposition method to grow a large-area hexagonal boron nitride film, selects a 6-inch silicon carbide (SiC) single crystal as a substrate material, and includes the following steps:

[0025] Step S1: In a vapor deposition furnace, a graphite fixture is used to fix the SiC substrate and the vacuum is evacuated to 10 -3 Pa pressure or less;

[0026] Step S2, using resistance heating to raise the system temperature to 1600°C and keep it warm. In a high temperature environment, two raw material gases, BCl3 and NH3 (or BF3 and NH3), are introduced at a volume ratio of 1:0.9, so that the two raw material gases BCl3 and NH3 (or BF3 and NH3) enter the deposition chamber from the bottom.

[0027] Step S3, turn off the power, cool the hexagonal boron nitride film and the substrate to room temperature and then take them out of the furnace, peel off the hexagonal boron nitride film from the substrate, and obtain the large-area hexagonal boron nitride single-photon source of the present invention.

[0028] In step S2 of this embodiment, the high temperature causes the graphite fixture to slightly decompose, thereby providing a small amount of carbon source. In the middle of the deposition chamber, the gases mix and react chemically to grow a large area of ​​hexagonal boron nitride film with carbon defects. The growth time of the hexagonal boron nitride film is about 90 minutes.

[0029] In the present invention, after reaction growth, the hexagonal boron nitride material can be uniformly deposited on the surface of the SiC substrate to form a large area of ​​high-quality h-BN film. The actual picture of the 6-inch h-BN film after peeling off from the substrate is as follows: Figure 1 a. The thickness of the h-BN film of the present invention can reach micrometer level, making it easy to peel off. Therefore, the method of the present invention can not only synthesize a uniform h-BN layer on a large-area substrate, but also control the thickness and crystal quality of the h-BN film by controlling the reaction conditions, providing a reliable preparation technology for its application in electronic devices and other high-performance materials.

[0030] Example 2: CL spectrum analysis of large-area hexagonal boron nitride single-photon source

[0031] The CL spectrum structure analysis of the large-area hexagonal boron nitride single-photon source of the present invention was performed using a scanning electron microscope. The results are as follows: Figure 1 b~ Figure 1 c, where Figure 1 b is the CL spectrum of hexagonal boron nitride film. Figure 1 c is the second-order time correlation function.

[0032] The results show that the unique way in which electrons excite the optical material produces a special fingerprint in the photon statistics of the emitted cathodoluminescence (CL) light. Measuring the CL spectrum, it can be seen that at room temperature the sample exhibits sharp peaks at 4.08eV, 3.93eV, 3.74eV, and 3.56eV, and a larger broad peak at 3.19eV (see Figure 1 b). These spectral features indicate that there are multiple energy levels and recombination centers inside the material, which can emit photons of specific energy under electronic excitation. For the 4.08eV emission line, the study shows that it is related to the nitrogen position (C N) is related to the carbon substitution impurities on the substrate. It is worth mentioning that a graphite fixture is specially customized in the deposition chamber to fix the substrate. At high temperature, the surface of the graphite fixture is slightly decomposed, thus providing a small amount of carbon source during the h-BN growth process.

[0033] To further investigate the luminescence characteristics, the Hanbury Brown-Twiss (HBT) correlator was used to measure the luminescence characteristics in the range of 3.6-4.1 eV. By measuring the second-order correlation function The statistical properties of photons and the quantum properties of light fields can be analyzed. In particular, the observation of g (2) (0)Satisfy 0≤g (2) (0)<1, which means that the photon statistics at zero delay time have a sub-Poisson distribution. After further deducting the background noise, g (2) (0)~0.2. This result is a clear sign of antibunching of photons in a quantum light field, reflecting that the photons in the light field are anti-correlated in time, that is, the probability of emitting two or more photons at the same time is extremely low (see Figure 1 c) This anti-bunching phenomenon is an important feature that distinguishes it from the classical light field, indicating that the luminescence center in the sample has the ability to emit single photons and has potential application value as a single-photon source.

[0034] Example 3: TEM crystal structure analysis of large-area hexagonal boron nitride single-photon source

[0035] The crystal structure of the large-area hexagonal boron nitride single-photon source of the present invention was analyzed using a transmission electron microscope (TEM). The cross-sectional high-resolution TEM image of the h-BN film is shown in FIG. Figure 2 shown.

[0036] Figure 2 It can be seen from the cross-section that the h-BN layered atoms are arranged very flat, showing its (002) crystal plane. This indicates that the film grows along the c-axis. This flat surface and clear atomic-level structure show that the sample has good crystal quality and uniformity. High-quality crystal structure has a crucial impact on the performance of h-BN samples in electronic and optoelectronic applications.

[0037] In summary, the present invention uniformly deposits a large area of ​​high-quality h-BN film on a SiC substrate by precisely controlling the chemical vapor deposition process conditions, which not only ensures the high crystal quality and large-area uniformity of the h-BN material, but also systematically studies its optical and quantum properties. CL spectrum measurements show that at room temperature, the h-BN material has sharp emission peaks at 4.08eV, 3.93eV, and 3.74eV. These peaks correspond to specific emission centers inside the material, indicating that it has the potential for single-photon emission. In order to further confirm the single-photon characteristics of these emission centers, an HBT correlator was used to measure the luminescence characteristics in the range of 3.6-4.1eV. By calculating the second-order correlation function g (2) (τ), especially the value g at zero delay time (2) (0), found g (2) (0)~0.2, which is much smaller than the lower limit of the classical light field of 1. This result shows that these emission centers in h-BN exhibit obvious photon antibunching characteristics, confirming their ability to serve as ultraviolet single-photon sources.

[0038] Therefore, the present invention not only demonstrates the feasibility of synthesizing high-quality h-BN films on large-area substrates by chemical vapor deposition, but also reveals the great potential of h-BN materials in the field of quantum optics. As a source of ultraviolet single-photon emission, h-BN materials are expected to play an important role in future quantum communications, quantum computing, and advanced optoelectronic devices. Such single-photon sources have irreplaceable application value in quantum information processing, quantum key distribution, and photon quantum computing, marking a major advancement in the application of h-BN materials in quantum technology.

[0039] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the protection scope of the present invention.

Claims

1. A method for preparing a large-area hexagonal boron nitride ultraviolet single-photon source, characterized in that: The following steps are involved: Step S1: In a vapor deposition furnace, a graphite fixture is used to fix the silicon carbide substrate and the vacuum is evacuated to 10 -3 Pa pressure or less; Step S2, using resistance heating to raise the system temperature to the reaction temperature and keep it warm; in a high temperature environment, two raw material gases, BCl3 and NH3, or BF3 and NH3, are introduced. The high temperature causes the graphite fixture to slightly decompose, thereby providing a small amount of carbon source. In the middle of the deposition chamber, the gases mix and react chemically to grow a large area of ​​hexagonal boron nitride film with carbon defects; Step S3, turn off the power, cool the hexagonal boron nitride film and the substrate to room temperature and then take them out of the furnace, peel off the hexagonal boron nitride film from the substrate, and obtain a large-area hexagonal boron nitride single-photon source.

2. The method for preparing a large-area hexagonal boron nitride ultraviolet single-photon source according to claim 1, characterized in that: The growth time of the hexagonal boron nitride film in step S2 is 80 to 120 minutes.

3. The method for preparing a large-area hexagonal boron nitride ultraviolet single-photon source according to claim 1, characterized in that: In step S2, the system is heated to 1500-1700° C. and kept warm.

4. The method for preparing a large-area hexagonal boron nitride ultraviolet single-photon source according to claim 1, characterized in that: In step S2, the volume ratio of the two raw material gases BCl3 and NH3, or BF3 and NH3, is 1:0.

9.

5. The method for preparing a large-area hexagonal boron nitride ultraviolet single-photon source according to claim 1, characterized in that: In step S2, two raw material gases BCl3 and NH3, or BF3 and NH3, enter the deposition chamber from the bottom.

6. A large-area hexagonal boron nitride ultraviolet single-photon source, characterized in that: The large-area hexagonal boron nitride ultraviolet single-photon source is prepared by the preparation method of any one of claims 1 to 5.

Images